U.S. Pat. No. 4,099,822, issued to A. W. Carlisle et al. and assigned to the assignee of this application, discloses a modular connector for joining large groups of wires. This connector has rearrangeable components capable of being separated and joined with other components to effect connections between different groups of wires. As a result, this connector is ideal for new equipment installations, equipment retrofits, in-service equipment cutovers, and equipment moves for reuse in telephone central offices.
The capability of this connector, however, depends in large part on the slotted or orbifurcated beam contact element used to make the occasional reconnects necessary during the life of any central office equipment. The contact element must permit a number of reliable electrical connections, say ten, with any given wire at the same point.
The contact element disclosed in Carlisle et al. is made of a high strength conductive material, such as a spinodal Cu-Ni-Sn alloy, in accordance with the method disclosed in U.S. Pat. No. 4,136,628. It is configured to be sufficiently gentle to allow multiple insertions of a given wire at the same point. Also, the contact element is contoured with constant strength furcations to have sufficient elasticity to accommodate a wide range of conductor sizes, i.e. 22-26 gauge, without permanent deformation or misalignment of the furcations.
However, there is room for improvement of the contact element disclosed in Carlisle et al., which is configured for penetrating the typical soft plastic insulation, such as polyvinyl chloride (PVC), on a wire. In telephone central offices, wire insulations other than the relatively soft and thin PVC insulation are found. Because of the more abrasive environments encountered by some wires, conductors are sometimes surrounded by a thicker insulation jacket comprising an inner layer of polyvinyl chloride (PVC) and a tough outer layer of cotton lacquered serving (CL). Cotton lacquered serving is historically difficult to displace with a slotted beam contact element.
With the contact element disclosed in Carlisle et al, a conductor with the typical soft plastic insulation needs to be inserted only once to effect a reliable first electrical connection. However, a conductor insulated with the PVC-CL insulation or other insulations having tough outer layers or just an extremely thick jacket of tough insulation, must be inserted twice to ensure complete penetration of the insulation to establish reliable electrical contact with the conductor for the first connection. Unfortunately, this requires that a craftsperson remember to make the double insertion for some first connections.
Hence, there is need for a slotted beam contact element which can penetrate the tough and thicker wire insulation, such as PVC-CL jacket, in one insertion and is effective with the typical PVC insulated conductor as well. At the same time, the slotted beam contact element needs to be sufficiently gentle on the wire to permit subsequent insertions.
Desirably, the contact element can still accommodate conductors having a wide range of gauges.
Also desirably, the contact element is inexpensive to manufacture.